The present invention relates to materials and packaging for use as expandable packaging, such as bags, for popping microwave popcorn.
Many microwave popcorn popping constructions in common commercial use are multi-ply paper bags in which inner and outer paper sheets are laminated to one another, with a microwave interactive construction (sometimes referred to as a microwave susceptor) encapsulated between the paper plies. Popcorn popping bags of this type are described, for example, in U.S. Pat. Nos. 4,904,488; 4,973,810; 4,982,064; 5,044,777; and 5,081,330, the disclosures of which are incorporated herein by reference.
A common feature of such constructions is that they are generally made from flexible paper materials. In this manner, the constructions are sufficiently flexible to open or expand conveniently under steam pressure, which forms when a popcorn charge therein is exposed to microwave energy in a microwave oven. Also, the packaging materials are sufficiently flexible to be formed from a sheet into a folded configuration, for example during a continuous bag-construction process.
Many microwave popcorn products include, within the package or bag, a charge of unpopped popcorn kernels, fat/oil (i.e., grease) and flavoring (for example salt). During storage or shipment, especially if the environment becomes relatively hot, the material stored within the bag can become liquefied and leak through the bag construction. Even when relatively high temperatures are not encountered in storage, some leakage can occur if the stored material includes a significant amount of flowable or liquefied oil/fat.
In addition, conventional microwave cooking of popcorn (especially when the popcorn charge includes fat/oil) results in the generation of hot liquid oil or fat. If the construction retaining the popcorn charge is paper, the paper must be sufficiently resistant to staining and to the passage of hot liquid oil/fat therethrough during the microwave cooking process to be satisfactory for performance of the product. For example, the oil/fat should not leak from the construction when the microwave cooking (i.e. popping) is undertaken. The construction should be sufficiently greaseproof or grease resistant so as to minimize an undesirable greasy feel or appearance on the outside of the package.
According to the present invention, a microwave popcorn package or bag is provided. The package generally comprises a flexible bag construction having inner and outer plies with the inner ply bonded to the outer ply by an adhesive present in an area as an adhesive pattern. The adhesive pattern is a pattern of polygons. Typically and preferably, the adhesive pattern is a pattern of evenly spaced filled diamonds or squares.
According to the invention, the adhesive is present as an adhesive pattern covering no more than about 50% of the surface area where the adhesive pattern is present. Typically, no more than about 40% of the area is covered, and preferably, no more than about 30% of the area is covered by adhesive. The area in which the adhesive pattern is present is at least about 80 square inches (516 cm2), generally at least about 100 square inches (645 cm2). Typically, the area is at least about 150 square inches (968 cm2), and preferably, the area is at least 200 square inches (1290 cm2). The adhesive pattern can cover the entire surface area of the ply, or the ply can have areas having a second adhesive pattern. The second adhesive pattern may be a continuous coating of adhesive, a discontinuous yet connected coating of adhesive, or may be a geometric pattern different than the major first adhesive pattern. The second adhesive pattern can be present, for example, as a perimeter border, or as a central area in which a microwave susceptor is positioned.
In one preferred embodiment, an adhesive pattern of equally spaced squares, which provides a coverage of 28%, covers the entire surface of the ply except for two areas of 3 square inches (19.4 cm2) that have continuous coverage of adhesive; thus the pattern covers about 241 square inches (1555 cm2). In another preferred embodiment, an adhesive pattern of equally spaced squares covers the entire surface of the ply at an adhesive coverage of about 28%.
In general, arrangements according to the present invention may be utilized to provide good effective microwave packaging, especially for popcorn, with savings over the amount of adhesive, and thus cost, utilized in many conventional arrangements.